Kilometers to astronomical units
Type a value in kilometers to see it in astronomical units straight away, or type in the second box to convert back.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Type the value in the kilometers box.
- Read the result in astronomical units as you type, and pick the precision you need.
- Swap the direction to convert back, or copy the result.
How it is calculated
au = km × 6.684587122e-9
Multiply the value in kilometers by 6.684587122e-9 to get astronomical units.
Example
To convert 25 km to astronomical units: 25 × 6.684587122e-9 = 1.67115e-7 au.
Conversion table
| Kilometers (km) | Astronomical units (au) |
|---|---|
| 1 | 6.68459e-9 |
| 2 | 1.33692e-8 |
| 3 | 2.00538e-8 |
| 5 | 3.34229e-8 |
| 10 | 6.68459e-8 |
| 20 | 1.33692e-7 |
| 25 | 1.67115e-7 |
| 50 | 3.34229e-7 |
| 100 | 6.68459e-7 |
| 250 | 0.00000167115 |
| 500 | 0.00000334229 |
| 1,000 | 0.00000668459 |
About the units
- Kilometer
- A kilometer is exactly 1000 meters and is the usual unit for road and travel distances.
- Astronomical unit
- The astronomical unit is exactly 149597870700 meters (IAU 2012), close to the mean Earth to Sun distance.
Limits and caveats
- Results are rounded for display and computed with the browser's floating point precision (about 15 significant digits).
- Both unit factors are exact by their official definitions.
Questions about this tool
How many astronomical units are in one kilometer?
1 km = 6.68459e-9 au exactly.
How do I convert kilometers to astronomical units?
Use au = km × 6.684587122e-9. For example, 25 km = 1.67115e-7 au.
How many kilometers are in one astronomical unit?
1 au = 149,598,000 km.
Are the inch, foot and mile factors exact or rounded?
They are exact by definition. Since the 1959 agreement one inch is exactly 2.54 cm, one foot 0.3048 m and one mile 1609.344 m.
What is the difference between a mile and a nautical mile?
A statute mile is 1609.344 meters and is used on roads. A nautical mile is 1852 meters and is used at sea and in aviation.